Grinding machine



Sept. 27, 1938.

A. L. KRAUSE GRINDING MACHINE Filed April- 6, 1957 Fig.1 V 270 TABLE CONTROLS TABCFSFEEIiY-T .M.

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GRINDING MACHINE Filed April 6, 1937 5 Sheets-Sheet 5 ,1 HR f/EADJTocx 7 mSPEED 2 cf m 9 75 M9 TART R q 7 u flfl/N 5 TARTER //v s E 5&5 01-6 23 R6 13 EXTRA sLow 8 1 82 TABLE SPEED fi L 5' 40 [1- 40 41 340 41 4' 4 Inventor y 1 f"? a;

Patented Sept. 27, 1938 PATENT OFFICE GRINDING MACHINE August L. Krause, Providence, R. I., assignor to Brown and Sharpe Manufacturing Company, a corporation of Rhode Island Application April 6, 1937, Serial No. 135,253

18 Claims.

The present invention relates to improvements in grinding machines, and more particularly to driving and control mechanism for a reclprocable grinding machine work table.

The invention is herein disclosed as embodied in a. cylindrical grinding machine of the general type set forth in the application of Mathewson and Krause, Serial No. 49,772, filed November 14, 1935, having a. longitudinally movable work table, a rotating grinding wheel, and a grinding wheel support movable toward and away from the table.

It is one object of the invention to provide in a machine of this general description, an improved electrical driving and control mechanism for the table, which is well adapted to provide a wide range of available grinding speeds including a number of very low table speeds for fine work.

'20 It is another object of the invention to provide a novel and improved wheel truing control for the machine which is constructed and arranged automatically to set up the machine for the performance of a truing operation without, 25. however, interfering with the normal setting of the several operating controls for grinding conditions, and more particularly to transfer the control of the operation of the work table to a truing control element having provision for ad- 30, justment to drive the table at any one of'a plurality of predetermined slow truing rates.

With these and other objects in view, as may hereinafter appear, the several features of the 1 invention consist in the devices, combinations and 35, arrangement of parts hereinafter described and claimed, which together'with the advantages to be obtained thereby, will be readily understood by one skilled in the art from the following description taken in connection with the accompanying 40 drawings, in which Fig. l is a view in front elevation of a grinding machine embodying the several features of the invention; Fig. 2 is an enlarged detail view of the extra slow table speed control switch with a part of the supporting panel broken 45 away to show the underlying switch construction;

Fig. 3 is a sectional view taken on the line 33 of Fig. 2; Fig. 4 is a developed plan view of the connections for the table including the table 'fastslow clutch; Fig. 5 is a sectional view taken on 5 the line 5-75 of Fig. 4; Figs. 6 and 7 constitute a wiring diagram of the electrical connections for the machine, Fig. 6 illustrating particularly the various controls for the machine and the electrical connections thereto which are mounted on 55 the machine control panel, and Fig. 'l ilhistrating the secondary switch and wiring connections through which the controls are operated to direct the operation of the machine; Fig. 8 is an explanatory diagram showing the line connections to certain of the machine motors and controls; 5 and Fig. 9 is an explanatory diagram illustrating particularly the direct current circuits energized by a direct current generator in the machine for controlling various phases of the machine operation. 10

The grinding machine disclosed in the drawings as embodying in a preferred form the several features of applicant's invention, comprises a. base I having mounted thereon a longitudinally movable work table I22 and a transversely movl6 able cross slide I24 on which is mounted a grinding wheel I28. The machine is provided with a tail stock generally indicated at I28 slidably mounted on the table I22 with a center I30 for supporting the work, and a head stock I32 which 0 may be of ordinary description, having a work centering device I34 which is positively driven by means of a head stock motor I36 supported integrally with the head stock I32.

The work supporting table I22 is driven from 25 a variable speed reversible direct current motor I38 as best shown in Figs. 4 and 5 of the drawings, through driving connections which comprise a pinion I40 mounted on the armature shaft I42 of the motor to mesh with a gear I44 secured 0 to a rotatable shaft I46. The gear I44 meshes also with a sleeve driving gear I48 which is externally supported in a bearing I50 and has formed at the inner or forward end thereof a clutch face I52 for engagement with a cooperating clutch surface I54 carried on the shiftable element of the table power-manual clutch. The shiftable clutch element referred to, takes the form of a shaft I56 supported for axial and rotational movements at one end within the sleeve hub of the gear I48, and at its other end in a bearing I" on the machine frame. Rigidly secured to the shaft I" is a high speed driving gear IIiII which has formed thereon the clutch face I54,

*and a slow speed driving gear I62.-

In order to provide for the manual operation of the table, there is formed on the end of the shaft I58, a clutch face I84 which is arranged to engage with a clutch member I66 formed on the adjacent end of a hand wheel shaft I10 in axial alignment therewith. The shaft I10 is supported in bearings H2 in the machine frame, and carries at its outer end a table traversing hand wheel I14. At its inner end the shaft I'III is provided with an axially extending pin I15 which extends into an axial bore in the abutting end of the shaft I56 to maintain the two shafts in axial alignment.

The gears I60 and I62 mesh respectively with gears I16 and H8 which are loosely mounted to turn on a rotatable shaft I80, and form respectively the fastand slow driving elements of a fast-slow clutch. A driven clutch member I82 is splined to the shaft I80 between the driving gears I16 and I18, and is arranged for axial movement in either direction to engage alternatively with cooperating clutch members formed on the adjacent faces of the driving gears I16 and H8. A pinion I84 also secured to the shaft I80 meshes with a gear I86 secured to a drive shaft E88 which also carries the table driving pinion I90, which in turn meshes with a. rack I92 (see Fig. 5) formed on the under side of the table I22. With this construction andarrangement of parts, it will readily be seen that the table may be connected alternatively for power or manual operation by an axial shifting of the power-manual clutch shaft I56 including the gears I60 and I62. The table may then be driven selectively at a high or low rate of speed either by power or armature 204 of the solenoid I94 by means of a" link 206 having a reduced portion which extends through a bore formed in a cross pin 208 supported in the forked lower end of the clutch lever I96. A yielding connection is provided between the clutch lever I96 and armature 204 by means of a compression spring 20I which is coiled about the reduced portion of the link I06 between a collar 2I2 on the end thereof and the cross pin 208, so that the lever I96 and cross pin 208 are held yieldingly against an abutting shoulder formed on the link 206. The fast-slow clutch I82 is normally held in its fast position by tension springs 2I4 which are connected at one end to a cross pin 2I6 on the lever I96, and at their other ends to a pin 2I8 on the machine frame. The movement of the clutch lever I96 in either direction is limited by means of adjustable stop pins 220 and "222 scr'w threaded into the machine frame.

The position of the power-manual clutch is similarly controlled by means of a forked clutch lever 224 having bearing blocks 226 which engage in a peripheral groove formed in the sleeve hub of the gear I 60. The position of the lever 224 and power-manual clutch is controlled by means of a spring (not shown) which tends to shift the clutch forwardly into hand feed position, and a solenoid illustrated at 228 in'th' wiring diagram Fig. 6, which acts when energized to move the clutch to power position. Inasmuch as the specific construction of the power-manual clutch shifting mechanism is fully illustrated in the application of Mathewson and Krause above referred to, being similar to that above described for shifting the fast-slow clutch E82, and forms specifically no part of the present invention, it is believed that no further illustration or description of this mechanism is necessary.

Reciprocation of the work table is controlled in the usual manner by table dogs 230 and 232 and a reversing lever 234 which is supported to turn on a stationary pivot 236, and operates through suitable switch connections to slow down and to reverse the direction of table travel. The construction and mode of operation of the switch connections for reversing the direction of table travel, are generally indicated in Fig. 6, in which the reversing lever 234 is illustrated in dot-anddash lines, supported to turn on the pivot 236, and having formed on a downward extension thereof, a rack 238 arranged for engagement with a pinion 240 to control the angular position of the switch cam 242 supported to turn therewith. Associated with the switch cam 242 are two vertically movableswitch members 244 and 246 which are rendered operative by the swinging movement of the reversing lever 234 from one limiting position to the other, to slow down and then to reverse the table motor. v

The cross feed mechanism of the present ma.- chine for moving the grinding wheel slide support 924 toward and away from the work, comprises a worm and nut assembly (not shown) which may be controlled manually by means of a cross feed hand wheel 250. Power operation of the cross feed is obtained by means of a ratchet 252 associated with the cross feed hand wheel 250, and a pawl 254 which is given a step-by-step reciprocation through a link 256(see Fig. 1) and a crank 258 carried on a rotatable shaft 260. The shaft 260 may be driven intermittently through one revolution with each table reciprocation by connections from the reversing lever 234 or continuously from the table motor I30 through gear connections including a shaft 262 (see Fig. 4),

bevel gears 264 and 266, and shaft I46. Inasmuch as these connections are fully described and. illustrated in the copending application of Mathewson and Krause above mentioned, and form specifically no part of the present invention, no further description of thismechanism is believed necessary.

The machine disclosed in the drawings is electrically driven and controlled through an electrical driving and control system which includes a number of electrical operating units, together -with switch control elements which are well adapted to control severally or collectively the several operating mechanisms of the machine in accordance with a number of operating cycles for the performance of different types of work on the machine.

Inasmuch as the electrical connections for the machine are in many respects identical with those illustrated and described in the copending application of Mathewson and Krause above referred to, these connections will be described only so far as believed necessary to illustrate the connection of the present invention therewith.

Certain features of applicant's invention are concerned with'improvements in the organization of the electrical control system to provide a wider range of readily available low table speeds for grinding when operating in accordance with any one of the several operating cycles for which the machine may be set up.

Other features of applicants invention relate specifically to an improved truing control which operates when rendered operative to shift the control of certain of the cooperating units of the machine to set up the machine for the truing operation, and more particularly which operatesto shift the table speed control to a table control element which is adjustable to drive the table at any one of a plurality of truing rates.

The electrical driving and control system for the machine, as best shown in Figs. 6 to 9 inclusive, of the drawings, comprises several alternating current motors including the main grinding wheel spindle motor 210, a coolant pump motor 212, a lubricant pump motor 214, a cross feed rapid movement motor 216, and a generator motor 218 which is in turn directly connected to drive a headstock motor generator 288 and a table motor generator 262. The headstock generator is a constant potential self-excited generator which supplies the necessary power for running the headstock motor I36, and also-supplies current to the direct current control circuit 7 and return wires 2, 4. In order to permit variaby means of a table control knob 304 which is hereinafter to be described, and to the fields of the several direct current motors and generators.

The several manually operable controls for the machine are mounted on a control panel 284 (see Figs. 1 and 6) which is mounted on the front side of the machine beneath the table. These controls include a machine start button 286 and a stop button 268 which operate to control the starting and stopping of the main spindle driving motor 210, the generator motor 218, the ol pump motor 214 and the coolant pump motor 212. The pushing of the start button 286 as shown in the electrical diagram Fig. 8, operates to close the contacts 15-83 to energize the starting switch solenoid 290 which in turn operates ,to close the main line contacts IL-85, l6-98 and IS-81, and also a holding switch contact |584. The pressing of the stop button 288 operates to open the contact 82-83 to de-energize the main switch'solenoid 290, and thus to stop the machine.

The starting of the generator motor 216 and headstock generator 280, operates immediately to supply current to the entire current control circuit which, asbest shown in the explanatory diagram Fig. 9, comprises a supply line I, 3, and a return line 2, 4. The headstock motor armature designated at 292 and the headstock motor shunt field 294 are connected across the supply tions in the motor speed, a headstock field rheostat HR is provided in series with the shunt field 284. This rheostat is controlled by means of a knob 286 on the left side of the panel 284 to determine the driving rate of the headstock motor.

The operation of the headstock is controlled by means of a headstock control knob 300 which may be rotated ina clockwise direction to close contact 4'I-48, and thereby to start the headstock in operation, and also to start the supply of coolant, and may be rotated in an opposite direction to open contact 43-44. and thereby to stop the headstock and shutoff the supply of coolant. The headstock knob may also be depressed to close contact 44-45, and thereby to jog the headstock motor at a slow rate. Inasmuch as these connections form specifically no part of the present invention, and are fully described in the application of Mathewson and Krause above referred to, no further description thereof is believed necessary.

The operation of the table may be controlled rotatable in a clockwise direction to start, the table motor and table, and rotatable in an opposite direction to stop the table motor and disconnect the power drive. The table knob may also be pressed downwardly by the operator to cause the table motor to be stopped and the table drive to be disconnected when the table reaches the end of its travel in the direction in which it is moving at the time of pressing the knob. As shown in dot-and -dash lines in the electrical diagram Fig. 6, the table knob 384 is rigidly secured to the upper end of a rotatable and axially movable switch control rod 306 which is connected to control the position of a table starting switch 308, a table stopping switch 3H), and an end stop switch 3 l 2. The operation of the table motor is controlle from the table knob 304 and the starting and stopping switches above described, by means of a number of secondary switch connections which include table dwell relays TR! and 'I'R2, generator field reversing contactors L and R, a hand wheel solenoid contactor HWS, under voltage contactor UV, table line and dynamic brake contactor LEI, counter electro-motive force relay CEMF, table slow speed contactor SS, and a table slow-down contactor resistance. The table dwell relays TRI and TR2 are carried on a panel 3M illustrated at the top of the wiring diagram Fig. 7, and the remaining of the above-mentioned switches are located on a panel 3l6 as best shown in Fig. 7.

The direction and rate of speed of the table motor I38 is determined by varying the direction and magnitude of the current in the field winding 328 of the table generator 282. Motor speed is controlled by a table speed rheostat which is connected in series with the table motor generator field 320, and comprises a resistance 322 and. an adjustableelement designated by the table speed control knob 324 located on the control panel 284 of the machine. In accordance with the present invention, there is also provided an additional rheostat control which is connected in series with the rheostat resistance 322, and is adjustable to secure a number of still lower table speeds. This additional control comprises a control knob 326 which when located in its central position, causes an addit onal resistance R6 to be placed in series with the main rheostat resistance 322 to produce a. minimum slow speed of operation of the table motor I33. In accordance with the calibration on the control knob 326, it may be assumed that the setting of this control in its intermediate position",

serves to provide a minimum low speed of seven inches of table travel per minute. Movement of the control knob 326 to the left will then operate to close the contact 23-36 to short-circuit a portion of the resistance R6, and thereby to increase the table speed to eleven inches per minute. Movement of the control knob 326 to the right, operates to close the contact 13-23 to wholly short-circuit the resistance R6, and thus to in- The setting of the table speed control knob 324 operating through the rheostat resistance 822 to control the speed of the table motor, may be rendered operative to secure an adjustment of table speed in accordance with a fast speed series or a slow speed series depending upon the position of the fast-slow clutch I82 above described. The position of the clutch I82 is controlled for power operation of the machine by means of a table power fast-slow selector switch 338 as best shown in Figs. 1 and 6 of the drawings, which operates when moved .to its' right hand or slow position to close the switch contact 3-13 to energize the slow speed contactor SS, which in turn closes SS contact 88-95 to energize the fast-slow clutch solenoid I54, causing the clutch I82 to be shifted to its slow speed position.

In accordance with one feature of applicant's invention, electrical connections are provided whereby the supplemental slow speed table control 326 is made available only with the slow speed series, and is rendered inoperative independently of the setting of the table speed control knob 324 when the fast-slow control knob 330 is moved to its fast position. To this end, a switch contact SS 23-! 3 is provided which is norm 11y closed to short-circuit the supplemental rheostat resistance R5, and is opened only when the slow speed contactor-SS is energized to shift the clutch I82 to slow speed position.

The manner in which the electrical connections above described operate to control table movement, is well illustrated in the following description of the operation of these connections to start, the table. In order to start the table, the table knob 304 is turned in a clockwise direction to close switch contacts 53-55 and simultaneously to open the contacts Ell-5i, thus energizing coil UV. Contact UV 61-68 closes, energizing LEI, and either L or R coil, depending upon the position of the reversing lever. It will be hereinafter assumed that coil R is energized. Contact UV. 22-23 closes, decreasing the table dynamic braking resistance, and contact UV 38-39 closes. energizing coil HWS, whichin turn energizes the solenoid 228 (diagrammatically indicated in Fig. 6) to disconnect the hand wheel from the table and engage the table drive to thetable motor I38. Contact LEI l1-I9 closes, starting the table motor and energizing coil CEMF, and the contact LEI 28-2i opens, disconnecting the dynamic braking resistor R4. Contact CEMF 3-38 closes, contact R 65-66 opens, thus preventing coil L from becoming energized, contact R 68-4 closes the holding circuit to the LEI and R coils, contact R 56-51 closes,energizing coil S to eliminate the table slow-down, and the contacts R "-15 and R I6-4 close, energizing the table generator field, so that the table will traverse to the right.

If it be assumed that the dwell control knob 334 shown in Figs. 1 and 9 of the drawings, is in its long dwell position, coil TRZ is energized.

Contact TR2 69-18 opens, and contact TR2 3-59 closes, energizing coil TRI. Contact TRI 18-4 opens, contacts TR2 69-10 and TRI 18-4 must both close before a table reversal can take place. Contact HWS 1I-12 opens, disconnecting the hand wheel fast-slow selector switch 336 shown in Figs. 1 and 6, and contact HWS 13-12 closes,

vplacing the power fast-slow selector switchin 33!]. Assuming now that it is desired to drive the table at a lower speed than that obtainable by the rheostat resistance 322, the control knob 324 is turned to its extreme position to the right in which the adjustable contact 3-l2 is wholly disconnected. The amount of resistance in the generator field circuit is now determined by the setting of the supplemental table slow speed selector switch 326 which, as previously pointed out, may be adjusted to drive the table at '1, 11 or 15 inches per minute. With this setting of the table speed controls, it will readily be seen that the closing of contact S l2-I3, will have no effect. It will also be noted that contact SS 23-I3 is opened only when the power fast-slow selector switch is in slow position to energize the slow speed contactor SS. If the. power fast-slow clutch is in its high speed position, the contact SS 23-l3 remains closed, short-circuiting the supplemental rheostat control 326, and causing the table to be driven at the minimum lowspeed obtainable with the minimum speed setting of the table speed control knob 324 in the high speed series.

For plunge cutting, the machine is provided with a plunge cut selector switch 340 which is mounted on the control panel 284. 348 operates when moved from inoperative to "plunge-cut position, to prevent movement of the table power-manual clutch I56 to power position, andthus to prevent the power operation of the table. This switch is provided particularly to set the machine for plunge cuts, so that during a plunge-cut operation the table cannot be inadvertently started by the manipulation of any of the several control elements which might otherwise operate to start table movement. The selector switch 340 is arranged to control contacts 38-31 and 55-51. For the run position of the switch 340, contact 38-31 is closed to provide a circuit to the solenoid contactor HWS,

and contact 55-51 is opened. When the switch,

improved truing control for the machine has been provided including means for shifting the control of the table to a table slow speed control element which may be adjustable to provide any one of a plurality of table truing speeds. The truing control comprises a truing knob 342 which is mounted on the control panel 284, and is arranged to be turned to the right to truing position, or alternatively to the left to an inoperative or grindping position; Associated with the truing knob 342 is a switch comprising a contact 3-34 which is arranged when closed to energize the truing speed contactor TS, and a contact 51-58 which is arranged when opened to de-energize the slowdown contactor S. With the switch in grind or inoperative position, contact 3-34 is opened, and

contact 51458 is closed.

The movement of the truing control knob 342 to truing position to energize the truing spec contactor TS, operates electrically to render in- The switch operative or to shift the control of the several operating units of the machine from the several manually operable controls, so that these units may be permitted to operate only in a manner consistent with the operation of truing the grinding wheel; The truing control herein disclosed, constitutes an improvement over that specifically set forth in the copending application of Mathewson and Krause above referred to, in which the table was made to travel at a single arbitrarily determined truing rate.' With the present construction, the control of the table speed is shifted by the operation of. the truing knob 342 to the supplemental table slow speed control knob 326 which is readily adjustable to provide any one of three slow feed rates for the table suitable for truing.

rough truing cut of the grinding wheel, and thereafter one or more fine truing cuts at either of the slower rates, and. thereby to effect a considerable savingin the time required for truing. The operator is enabled further to adjust the truing rate of the table travel more accurately to perform this operation at the highest speed consistent with eiiicient truing having regard for the type of wheel and the class of work to be performed thereby.

The functions performed by the truingcontrol include additionally the connecting of the coolant supply to be turned on upon the starting of the table reciprocation irrespective of whether the headstock motor is running or not. The fast traverse control knob 348 is rendered inoperative to cause the wheel spindle carriage to be either advanced or retracted. The table dwell mechanism is disconnected to eliminate any delay in table reversal; The plunge-cut selector switch 348 is disconnected so that it becomes unnecessary for the operator to shift the setting of this switch for truing as, for instance, where it is found necessary to interrupt a series of plungecut grinding operations to true the grinding wheel. The wheel spindle reciprocating mechanism is rendered inoperative to prevent reciprocation of the grinding wheel during the truing operation. The electrical connections controlled by the automatic hand wheel control selector switch 368 are disabled so that it becomes unnecessary for the operator to shift the'position of. the grinding wheel with relation to the truing tool 488.

The operation of the electrical connections to shift the control of the several operating units for truing the grinding wheel may be described as follows in connection with the electrical diagrams Figs. 6 to 9 inclusive. The operator turns the grind-truing selector switch 342 to true position, so that the contact 3-34 is closed to energize the truing speed contactor TS, and contact 61-68 is openedto de-energize the table slowdown contactor S. Contact S I2-I3 consequently remains open, so that the table speed control knob 324 is rendered inoperative, and the entire rheostat resistance 322 is maintained in series 75 with the table generator field 328. The speed at start the table.

which the table motor will now be driven during the truing operation, is determined by the setting of the supplemental table slow speed control knob 326, and is adjustable to any one of three speeds ranging from seven to fifteen inches of table travel per minute as above described. Contact TS 88-91 opens, breaking the circuit to the oscillator solenoid 354 diagrammatically shown in Figs. 7 and 8 of the drawings, thus making it impossible to oscillate the grinding wheel. Contact TS 32-4 opens, breaking the circuit to the F and B coils, to render the cross feed rapid movement control knob 348 inoperative to either advance or retract the wheel spindle carriage. The opening of the contact TS 32-4 also breaks the circuit through the control relay coil AR, thus rendering the knob automatic hand wheel selector switch 358 shown in Fig. 6, inoperative, so that the cross feed hand wheel 250 may be rotated to advance or retract the grinding wheel alone irrespective of the setting of the selector switch 356. Contact TS 38-3! closes, so that the power-manual clutch will be subject to the control of the table starting button irrespective of the position of the plunge-cut selector switch 340. Contact TS 38-40 closes, so that the pressing of the table start button will operate to energize the coolant control relay CS to turn on the supply of coolant. The contact TS 60-6I opens, deenergizing the table dwell relays TRI and TRZ to eliminate table dwell upon reversal. Contact TS 3-13 closes, so that the pressing of the table start button by energizing the coil HWS, will operate to energize the table slow speed contactor SS to shift the fast-slow clutch I82 to slow position irrespective of the setting of the power fastslow selector switch 330. At the same time, contact SS 23-l3 opens, so that the supplemental rheostat control element 326 is rendered operative to determine the actual truing rate of travel of the table.

As the next step in preparation for truing the grinding wheel, the operator will ascertain that the truing attachment is properly mounted on the machine table, and adjust the position of the grinding wheel with relation to the truing tool, and will then move the grinding wheel into proper relation thereto by manipulation of the cross feed hand wheel. The table reversing lever-234 is moved forwardly out of the path of the table dogs, so that the table can be moved past its usual stop position for the operation of the truing tool. The operator after having set the supplemental table speed control knob 326 to secure the desired truing rate of travel of the table, now turns the table controlknob 304 to start position, closing contact 63-56 to energize the under voltage contact UV. UV contact 33-48 closes, energizing coil HWS and coil CS through the closed TS contact 38-48. At substantially the same instant, contact HWS-13-I2 closes, energizing coil SS to shift the slow-fast clutch I82 to slow position. Contact HWS 88-84 closes, energizing the hand wheel solenoid 228, thus shifting the power-manual clutch I64 to power position to Contacts CS 88-92 and CS 82-83 close, energizing coolant solenoid which starts the coolant flowing. Contact SS 88-98 closes, energizing the slow speed solenoid 194 which operates the slow-fast clutch I82 to shift the table drive gear ratio to the slow speed series.

At the end of the truing op the operator turns the table control knob. 384 to stop position to open contact 44-43 to de-energize under voltage relay UV, causing the contacts ill the supply of coolant.

previously closed by the energizing 01' this coil, to open, de-energin ng the coilslZiEi, HWS, CS and SS to stop the toble motor, shift the power man ual clutch to hand wheel position, and shut oil The turning of the truing control knob to grinding position now operates to open contact ttt and close contact tl-Iid, thus de energizing the truing speed contactor 1353 and re-establishing the circuit to the slowdown contuctor S to shift the control of the several operating units of the machine hatch to the several manual controls on the machine.

The invention hoving been described, what is claimed is:

l. in a, grinding machine having a grinding wheel, a, grinding wheel support and a work sup port, driving means for imparting trsnslstory movements to one oi said supports including a rate changer having means for odjustment to drive the support at any one of a series of prede= terniincd rates, it supplemental rate changer on erative only in combination with the slowest speed adjustment of the first rate changer to drive the support ct any one oi s series oi slower rates, seporote manually operable menus for etiecting the odiustrnent of each ct sold rate clinngers, and means for shifting said first rate changer to the slowest speed adjustment independently oi the setting of its manual control means whereby to effect a shift in support movement from an adjusted rate in one series to odiusted rote in the other series.

2. in o grinding machine a reciprocat ing wort: table s grinding wheel carriage movable toward and away from the wort: table, driving means for the table including a rate changer having means for adjustment to drive.

the table at any one or a series of predetermined rates, a supplemental rate changer having means for adjustment to drive the table at any oneoi' a series of slower rates, wheel truing means carried by the table, and a truing control for the machine comprising a manually. operable selector device having alternative operative and oil positions, and connections therefrom for rendering said first mentioned rate changer inoperative and said supplemental rate changer operative to determine the rate of table travel.

3. In a grinding machine having a. reciprocable work table and a rotating grinding wheel, a.

grinding wheel carriage relatively movable toward and away from the work table, wheel truing means carried by the table, driving means for the table including a, rate changer adjustable to drive the table at any one of a series 01' predetermined rates, a supplemental rate changer adjustable to drive the table at any one of a series of slower rates, and a wheel trulng 011M301 for the machine comprising a. selector device having alternative trulng and oi! positions, and connectlops rendered operative by the movement of said selector device to trulng position to render said first mentioned rate changer inoperative and said latter rate changer operative to determine the rate of table movement. 4. In a. grinding machine having a reciprocal)! work table, a rotating grinding wheel, and a grinding wheel, carriage relatively movable toward and away from the work table, a.- variable speed electric motor, a variable speed motor control having means ior adjustment to drive the motor at any one 01' a series of predetermined rates, connections for driving the table from the motor including a. fast-slow clutch, means to:

, shifting the clutch, anda supplemental variable speed motor control operative for one position only oi said first-mentioned motor control and.

having means for adjustment to drive the motor at any one of a' series of slower rates.

5. In a grinding machine having a reciprocable worlr. table, a rotating grinding wheel and a grinding wheel carriage relatively movable to ward and away from the worlr table, wheel truing means carried by the table, a variable speed' electric motor, a rate changer having means for adjustment to drive the motor any one of a series otpredetermined rates, and connections for driving the table from the motor including o fost- SlOW clutch, means for shifting the clutch, a second rate, changer supplemental to said firs t-rnentioned rate changer having means tor adjustment to drive the motor at stay one of e series of we determined slower rates, and s. wheel truing control tor the machine comprising a selector device having alternative inning and inoperative positions, and connections rendered operative by the movement of said selector device to truiug position to shift said clutch to slow position, ren

der sold first-=mentioned rate changer inoperative,

and sold letter rate changer operative to determine the rate of table movement.

in grinding mochine having a reciprocahle worh table, a rotating grinding wheel and a grinding wheel carriage relatively movable toward and away from the work table, driving means for the tohle including a variable speed electric motor, rheostet for controlling the motor speed including o resistance and a, manually operable control element having an off position and o plurality of adjustable speed positions to drive the tel ale at any one ot a series of predetermined rates, e, supplemental rheostat connected in series with said resistance and independently of said control element, adjustable to drive the table at any one of a series of predetermined slower rates, and aswitcli connection for operatlvely connecting and disconnecting said control element whereby to effect a. shift in motor speed from an adjusted rate in one series to an adjusted rate in the other series.

7. In a. grinding machine having a rcclprocable work table, a rotating grinding wheel and a grinding wheel carriage relatively movable toward and away from the work table, on electric motor for driving the table, a. rheostat for controlling the motor speed including a-reslstance and a manually operable control element having an off position and a plurality'of adjustable speed positions to drive the table at any one of a series of predetermined rates, a. supplemental rheostat connected in series with'said resistance and independently of said control element adjustable to drive the table at any one of a series of predee termined slower rates, a wheel trulng control for the machine comprising a selector device having alternative trulng and inoperative positions, and connections rendered operative by the movement of said selector device to trui'ngpositlon to electrically disconnect said control element and thereby to render said supplemental rheostat operative to determine the rate of table move ment.

8. In a grinding machine having a reciprocable work table, a rotating grinding wheel, and a grinding wheel carriage relatively movable toward and away from the work table, a variable speed electric motor, a variable speed motor control having means for adjustment to drive the motor at any one of a series 01' predetermined rates, a supplemental variablespeed motor. control having means for adjustment to drive the motor at any one of a series of slower rates, connections for driving the table from the motor including a fast-slow clutch, means for shifting the 'clutch, and means controlled by said shifting means to render said supplemental motor control inoperative upon movement of the clutch to fast position. i I

9. In a grinding machine having a 'reciprocable work table, and a grinding wheel carriage relatively movable toward and away from the work table, an electric motor-tor driving the table, a rheostat for controlling the motor speed including a resistance and a manually Operable control element havingan of! position and a plurality of adjusted speed positions to drive the table at any one of a series of predetermined rates, a supplemental rheostat connected in series with said resistance and independently of said control element adjustable to drive the table at any one of a series of slower rates, a fast-slow clutchshiftable for driving the table from the motor in accordance with a fast or slow speed series, and means operable to render said supplemental rheostat inoperative to control table speed upon shifting said clutch to fast position.

10. In a grinding machine having a reciprocablework table, and a grinding wheel carriage reltively movable toward and away from the work table, a variable speed reversible electric motor and connections including a clutch for reciprocating the table, a manually operable table starting and stopping control including connections for starting and stopping the motor and simultaneously for engaging and disengaging the clutch, a manually operable control for adjusting the motor speed, a secondary motor control for adjusting the motor to a series of lower speeds, a plunge out control device including a manually operable plunge out control switch movable to disable said electrical connections for engaging the clutch, wheel truing means carried by the table, a wheel truing control for the machine comprising a manually operable selector device for alternative truing and oil positions, and electrical connections rendered operable by the movement of said truing control to truing position to connect the table starting and stopping control to engage the clutch independently of the setting of the plunge out switch, and to operatively disconnect said motor control and to connect said secondary motor control of table travel.

11. In a grinding machine having a reciprocable work table and a rotating grinding wheel, truing means carried by the table, means ior reciprocating the table comprising a reversible variable speed electric motor, a variable 'speed motor control having means for adjustment to drive the motor at any one of a series of predeterinined rates, a .supplemental variable speed motor control having means for adjustment to drive the motor at any one of a series of slower rates, a table reversing circuit including braking and reversing switch connections for the motor. electrical means for delayingthe operation of said reversing switch to provide a dwell in the table movement upon reversal, a truing control for the machine comprising a selector device having alternative truing and of! positions, and switch connections rendered operative by the movement of said selector device to truing position for disconnecting said electrical means and thereby to eliminate the dwell, and to render said first mentioned motor controlinoperative and to determine the rate said latter supplemental motor control operative to determine the rate of table movement.

12. In a grinding machine having a reciprocable worl; table, a grinding wheel carriage relatively movable toward and away from the table, wheel truing means carried by the table, power means for reciprocating the table, a manually operable control to start and stop table reciprocation, a rate changer having means for adjustment to drive the table at any one of a series of predetermined rates, a supplemental rate changer having means foradjustment to drive the table at any one of a plurality oi. slower rates, a plunge cut controidevice including a manually operable element movable to prevent the operation of said manually operable control to start the table, a wheel truing control for the machine comprising a selector device having truing and off positions, and connections controlled thereby to disconnect said plunge out control device, to reestablish said table starting and stopping control, to render said first-mentioned rate changer inoperative and said supplemental rate changer operative to determine the rate of table movement.

13. In a grinding machine having a reciprocable work table, and a grinding wheel carriage reciprocation, a variable speed motor control having means for adjustment to drive the motor at anyone of a series of predetermined rates, a supplemental variable speed motor control having provision for adjustment to drive the motor at any one of a plurality of slower rates, a wheel truing control for the machine comprising a selector device having alternative truing and inoperative positions, and connections rendered operative by the movement 01' said control to truing position to render said means for slowing the motor inoperative and to render said former rate charger inoperative and said supplemental rate changer operative to control the rate of table movement. I

14. In a grinding machine have a reciprocable work table, and a grinding wheel carriage relatively movable toward and away from the table, wheel truing means carried by the table, a variable speed reversible electric motor for driving the table, means for reversing the motor to reverse the direction of table drive, avariable speed motor control having means for adjustment to drive the motor at any one of a series or predetermined rates, a supplemental variable speed motor control having provision for adjustment to drive the motor at any one of a plurality oi! slower rates, connections for driving the table from the motor including a fast-slow clutch, means under the control of the operatorior determining the position of the clutch, means for prior to reversal, means undenthe control of the operator for starting and stopping the table reciprocation, a wheel truing control for the machine comprising a manually operable selector device having alternative truing and of! positions, and connections rendered operative by the movement of said control to truing position to render slowing the motor to a predetermined slow rate said means for slowing the motor inoperative, to 75 shift said clutch to slow position, and to opera tively connect said supplemental motor control to operate the motor at any one or said slower rates. i

15. Ina grinding machine having a grinding wheel, a grinding wheel support, a work support, and wheel truing means carried by said work:

support, a variable speed electric motor, driving means for imparting translator-y movements one of said supports including a variable speed electric motor, a rate changer having means for. ad= justment to drive'the motor at any oi a series of predetermined rates, and connections for driving said support from the motor including a last; slow clutch, means for shifting the clutch, secnd rate changer supplemental to said first mem tioned rate changer having means for adjustment to drive the motor at any one oi a series or" predetermined slower rates, and a wheel truing: ccn= trol for the machine comprising a selector device having alternative truing and inoperative posi=- tions, and connections rendered operative hy the movement oi said selector device to truins posi== tion to shift said clutch to slow position, to render said first-rnentioned rate changer inoperative, and, said latter rate charger operative to deter mine the rate of support movement.

it. In a grinding machine having grinding wheel, a grinding wheel support and a worlr support, driving means for imparting .translatory movement to one or" said supports including an electric motor for driving said support, a rheostat for "controlling the motor speed including a re= sistance and a manually operable control element having an off position and a plurality of adjustable speed positions to drive the support at any one of a series of predetermined rates, a supplemental rheostat connected in series with said resistance and independently 01' said control element adjustable to drive the support at any one of a series of predetermined slower rates, a wheel truing control for the machine comprising a selector'device having alternative truing and inoperative positions, and connections rendered operative by the movement or said selector device to truing position to electrically disconnect said control element and thereby to render said supplemental rheostat operative to determine the rate of support movement.

aisnrov l7. In a grinding machine having a grinding wheel, a grinding wheel support and a work support, driving means for imparting translatory movements to one of said supports including a variable speed electric motor, a variable speed motor control having means for adjustment to drive the motor at any one oi a series of predetermined rates, a supplemental variable speed motor control having means for adjustment to drive the motor at any one of a series of slower rates, connections for driving the support from the motor including a fast-slow clutch, means for shifting the clutch, and means controlled by said shiftinc means to render said supplemental motor control inoperative upon movement oi the clutch to last position.

iii. In a grinding machine having a grinding wheel, a grinding wheel support, a work support, and wheel truing means carried by the work support, driving means ior imparting translatory movements to one of said supports including a variable speed reversible electric motor for driving said support, means for reversing the motor to reverse the direction of support drive, a variable speed motor control having means for adjustment to drive the motor at any one or a series of predetermined rates, a supplemental variable speed motor control having provision for adjustment to drive the motor at any one of a plurality of slower rates, connections for driving the support from the motor including a fast slow clutch, means under the control of the operator for determining the position of the clutch, means for slowing the motor to a predetermined slow rate prior to reversal, means under the control of the operator for starting and stopping the support reciprocation, a wheel truing control for V the machine comprising a manually operable se- 

